Fuel cells are devices that directly convert chemical energy of reactants, i.e., fuel and oxidant, into direct current (DC) electricity. In general, fuel cell technology includes a variety of different fuel cells, such as alkali fuel cells, polymer electrolyte fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, solid oxide fuel cells and enzyme fuel cells. Fuel cells generally run on hydrogen (H2) fuel, and they can also consume non pure hydrogen fuel. Non pure hydrogen fuel cells include direct oxidation fuel cells, such as direct methanol fuel cells (DMFC), which use methanol, or solid oxide fuel cells (SOFC), which use hydrocarbon at high temperature. Hydrogen fuel can be stored in compressed form or within compounds such as alcohols or hydrocarbons or other hydrogen containing materials that can be reformed or converted into hydrogen fuel and byproducts. Hydrogen can also be stored in chemical hydrides, such as sodium borohydride (NaBH4), that react with water or an alcohol to produce hydrogen and byproducts. Hydrogen can also be adsorbed or absorbed in metal hydrides, such as lanthanum pentanickel (LaNi5) at a first pressure and temperature and released to fuel a fuel cell at a second pressure and temperature.
Most hydrogen fuel cells have a proton exchange membrane or polymer electrolyte membrane (PEM), which allows the hydrogen's protons to pass through but forces the electrons to pass through an external circuit, which advantageously can be a cell phone, a personal digital assistant (PDA), a computer, a power tool or any device that uses electron flow or electrical current. The fuel cell reaction can be represented as follows:
Half-reaction at the anode of the fuel cell:H2→2H++2e−
Half-reaction at the cathode of the fuel cell:2(2H++2e−)+O2→2H2O
Generally, the PEM is made from a polymer, such as Nafion® available from DuPont, which is a perfluorinated sulfonic acid polymer having a thickness in the range of about 0.05 mm to about 0.50 mm, or other suitable membranes. The anode is typically made from a Teflonized carbon paper support with a thin layer of catalyst, such as platinum-ruthenium, deposited thereon. The cathode is typically a gas diffusion electrode in which platinum particles are bonded to one side of the membrane.
For DMFC, the chemical-electrical reaction at each electrode and the overall reaction for a direct methanol fuel cell are described as follows:
Half-reaction at the anode:CH3OH+H2O→CO2+6H++6e−Half-reaction at the cathode:1.5O2+6H++6e−→3H2OThe overall fuel cell reaction:CH3OH+1.5O2→CO2+2H2ODMFCs are discussed in U.S. Pat. Nos. 4,390,603 and 4,828,941, which are incorporated by reference herein in their entireties.
In a chemical metal hydride fuel cell, potassium or sodium borohydride is reformed and reacts as follows:NaBH4+2H2O→(heat and/or catalyst)→4(H2)+(NaBO2)Suitable catalysts for this reaction include platinum and ruthenium, and other metals. The hydrogen fuel produced from reforming sodium borohydride is reacted in the fuel cell with an oxidant, such as O2, to create electricity (or a flow of electrons) and water by-product, illustrated above. Sodium borate (NaBO2) by-product is also produced by the reforming process. A sodium borohydride fuel cell is discussed in U.S. Pat. No. 4,261,956, which is incorporated by reference herein in its entirety.
Pressure regulators and other fluidic flow control devices are needed to control or regulate the flow of fuel from fuel cartridges or fuel storages to fuel cell systems, fuel refilling devices and the devices that fuel cells powered. The known art discloses various pressure regulators and flow control devices. A need, however, exists for improved pressure regulators and flow control devices. To a certain extent, this need has been addressed by commonly owned U.S. Pat. No. 8,002,853 and its progenies, U.S. published patent application nos. 2010/0104481, 2011/0189574 and 2011/0212374. These patent documents are incorporated herein by reference in their entireties.